Fix lints and errors in fidl format code.

Change-Id: I21df9115e4aca73044422e2cca3543b89f071359
diff --git a/src/tool_finder.ts b/src/tool_finder.ts
index ef1cb49..bb1ec03 100644
--- a/src/tool_finder.ts
+++ b/src/tool_finder.ts
@@ -30,14 +30,13 @@
  */
 function deriveZirconOutPath(fuchsiaRoot: string): string | null {
     const buildOutputPointer = path.join(fuchsiaRoot, '.fx-build-dir');
-    let outputRoot
     try {
-        outputRoot = fs.readFileSync(buildOutputPointer, { encoding: 'utf8' }).trim();
+        const outputRoot = fs.readFileSync(buildOutputPointer, { encoding: 'utf8' }).trim();
+        return path.join(fuchsiaRoot, outputRoot + '.zircon');
     } catch (err) {
         // TODO: proper error handling
         return null;
     }
-    return path.join(fuchsiaRoot, outputRoot + '.zircon');
 }
 
 /**
@@ -103,7 +102,7 @@
 
         const basePath = path.dirname(uri.fsPath);
         const toolPath = findFidlFormatInFolder(basePath);
-        if (toolPath == null) {
+        if (toolPath === null) {
             continue;
         }
 
@@ -137,7 +136,7 @@
         // Traverse through parent repositories until the direct child of the
         // root directory.
         for (folderPath = folder.uri.fsPath;
-            path.dirname(folderPath) != folderPath;
+            path.dirname(folderPath) !== folderPath;
             folderPath = path.dirname(folderPath)) {
 
             const toolPath = findFidlFormatInFolder(folderPath);
@@ -166,13 +165,12 @@
     let formatTool: string | undefined | null
         = vscode.workspace.getConfiguration('fidl').get('formatTool');
 
-    try {
-        fs.accessSync(toolPath, fs.constants.X_OK);
-    } catch (err) {
-        throw new FormatToolError(FormatToolErrorCause.ToolNotExecutable);
-    }
-
     if (formatTool) {
+        try {
+            fs.accessSync(formatTool, fs.constants.X_OK);
+        } catch (err) {
+            throw new FormatToolError(FormatToolErrorCause.ToolNotExecutable);
+        }
         return formatTool;
     } else {
         return null;